Japanese Laid-Open Patent Publication No. 2008-121244 describes an example of a conventional sliding plug door device for a railway vehicle. The plug door device includes a plug door opening-closing apparatus that performs an operation for moving doors in the width direction of a railway vehicle when sliding the door in the front-rear direction of the railway vehicle, that is, the so-called plugging operation. The plug door device includes a lock mechanism that restricts movement of the doors in the vehicle front-rear direction and the width direction when the doors are completely closed and completely cover an entrance located in a vehicle side wall.